The present invention relates to control valves generally, and specifically pertains to sliding spool control valves having a trip action which may be used to rapidly shut down a steam turbine, or the like, if an emergency condition develops.
Generally, large turbines are brought up to speed and shut down in a rather gradual manner. However, it sometimes becomes necessary to rapidly shut down such machinery in the event of an emergency condition.
While existing control valves are satisfactory for controlling such large turbine machinery under normal conditions, it would be desirable if a control valve were provided which incorporated a trip feature for very rapidly shutting down a turbine. It would be further desirable, if such a valve arrangement were provided which operated without mechanical springs.
Spool valves are currently known which generally incorporate hydraulic pressures acting on various flanges and surfaces formed thereon to position the spool with respect to critically positioned valve ports. Such spool valves control equipment but none are known to have a springless trip action of the type contemplated herein.
A typical example of an existing spool valve is covered by U.S. Pat. No. 2,610,647 which shows a pilot operated pressure control valve. The action of the valve results in the maintenance of a constant pressure in a fluid line. The device does not incorporate a snap action dump feature which is operative without the use of mechanical springs.